Method and device for image guided dynamic radiation treatment of prostate cancer and other pelvic lesions
A method and device for image guided dynamic radiation treatment of prostate cancer and other pelvic lesions including: 1) a unique fan geometry of radiation sources; 2) a special collimation method and apparatus to sculpt the radiation borders; 3) an integrated three-dimensional imager and a special tissue interface imaging system to locate and track critical boundaries in real-time; 4) a dynamic patient support system, which is shared by the said imager and the irradiation system; and 5) motorized custom shielding filters to further protect neighboring normal tissues such as the kidneys and femoral heads. The fan geometry utilizes a plural number of radiation sources arranged specifically for irradiating tumors in the human pelvis while not harming critical structures, and the collimation sculpts the radiation borders using motorized shields for different sensitive structures. This allows high doses of radiation to be delivered to lesions within the human pelvis, such as the prostate, while sparing its surrounding structures, such as the rectum and bladder, as well as the urethra that is contained inside the prostate.
The present application derives priority from U.S. provisional patent application Ser. No. 61/210,766 filed 23 Mar. 2009.BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a method and system for delivering radiation treatments to cancerous tissues within the human pelvis, such as the prostate gland and the cervix, while avoiding tissues that would otherwise be damaged by aggressive radiation treatment.
(2) Description of Prior Art
Radiation therapy and radiosurgery are established methods of treating patients with certain malignant and benign diseases. Radiotherapy is typically given over many episodes of treatment and generally involves treating larger volumes of tissue that often include normal structures that may be affected adversely by the radiation treatment. The strategy of spreading the therapy over many episodes separated in time is chosen to enable recovery of normal tissues included in the treatment volume. It is assumed that recovery of normal tissue occurs at a faster rate than that for cancerous tissue. Radiosurgery is typically given in one or a few episodes of very precise treatment to small volumes of diseased or affected tissue with the intent to destroy all tissue contained within the treatment volume.
Toxicity to normal structures limits the radiation dose and the treatment efficacy of both methods as normal structures may be contained within or adjacent to the diseased tissue. A normal structure within the prostate gland is the urethra. The normal tissues in proximity to the prostate gland are illustrated in
Prostate cancer is known to be slow growing and resistant to conventional treatment which is given by applying many small doses of radiation. Hypofractionation or a few large doses of radiation has been demonstrated to be more effective in killing cancerous cells for the same amount of energy deposited. However this approach causes unacceptable toxicities such as urethral stricture or even tissue necrosis. Although in theory we know that a higher daily dose is more effective for curing prostate cancer. However, daily dose greater than a 3Gy dose using external beam radiation has not been widely used because of urethra necrosis. Martinez et al. used radioactive seeds interstitially introduced to the prostate to deliver more than 10.5Gy daily dose to prostate and was found to be very effective. Vicini et al., High Dose Rate Brachytherapy In The Treatment Of Prostate Cancer, Journal World Journal of Urology, vol. 21, no. 4 (Sept. 2003), pp 220-228.
Because Vicini et al. used “peripheral loading”, i.e., placing more radioactivity at the periphery of the prostate and avoiding high dose to the urethra, the toxicity from their interstitial high dose rate treatment was found to be low. However, their method has the greatest detriment of being very invasive and must be performed under general anesthesia. The present inventors do not know any method that can safely deliver a daily dose of greater than 3Gy using external beam radiation without damaging the urethra. Note that, although prostate cancer is used as an example, the method disclosed in this invention is not limited to the treatment of prostate cancer. There has not been any method that can safely deliver a high dose to the target while sparing a critical structure completely surrounded by cancerous tissue.
There is no treatment machine that can optimally spare the urethra and other critical organs such as rectum and, bladder and seminal vesicles. Conventional Modern radiotherapy employing intensity modulation techniques provides better dose conformity to the prostate and less dose to the bladder and rectum, with a typical dose distribution illustrated in
There is no dedicated tele-radiotherapy machine specifically designed to treat prostate cancer using a single or an arrangement of radioisotopes or other source of high energy radiation.
Protons have also been used for prostate treatment. This is an extremely expensive and complex method and has not demonstrated any benefit in part due to the challenges mentioned above for conventional treatment.
Past efforts of intensity-modulated radiation therapy have been limited to the use of compensators or multi-leaf collimators to modulate the incident radiation beams. The treatment beam arrangement is generally coplanar with the axis of rotation in the cranial caudal dimension.
In the present application the inventors describe a treatment device with unique beam geometry and collimation technology that can sculpt a radiation pattern avoiding the urethra and bladder and rectum while covering the prostate gland with a higher radiation dose.
Similar past efforts in image guidance have been limited to pretreatment imaging or treatment monitoring using simple planar X-ray fluoroscopy. Pretreatment imaging can include ultrasound, CT scanning, MRI and MV or kV planar X-ray. In the case of pretreatment imaging the tissues are not represented in real time during the treatment and changes that occur are not observed. In the case of X-ray fluoroscopy at the time of treatment imaging is limited to boney landmarks or implanted markers as surrogates for target tissues. In this invention we outline a technology and method to detect and monitor relevant soft tissue interfaces during radiation treatment.
Radiation therapy using external beams as described above and illustrated in
Important features of the invention also include a practical method for real-time monitoring of the location of the critical structures and real-time adjustment of treatment parameters to spare these critical structures. This is again achieved through the extension of the definition of control points by associating with each control point a critical point of reference, which is a landmark on a critical structure that needs to be protected. For prostate treatment, we propose the use of an endorectal ultrasound probe to monitor the position of key interfaces, namely the urethra and the anterior rectal wall. For every control point that defines the treatment parameters at one time interval, there is a unique critical point of reference, which is normally the closest interface location. During delivery, the reference point for the next control point is updated during the delivery of the current control point based on the real-time imaging and real-time registration of the interface features between that acquired in real-time and that used for planning the treatment. Such updating of the locations of critical interfaces as the geometric reference of the control points allows the treatment to adapt to anatomy changes to protect the critical structures without changing the treatment plan.
Numerous clinical reports have established that the effects of radiation on urethra is a long-term process and the incidents of late effects increases with time over 20 years without a plateau. See, e.g., Miller et al., “Long-Term Outcomes Among Localized Prostate Cancer Survivors: Health-Related Quality-Of-Life Changes After Radical Prostatectomy, External Radiation And Brachytherapy”, Journal of Clinical Oncology (Vol. 23, No. 12: 2772-2780). The slope of increase is directly proportional to the fractional dose delivered to the urethra. To date, there is no radiation treatment machine that can deliver high doses of radiation to the prostate while being able to spare the urethra.
In view of the foregoing, it is an object of the present disclosure to provide a method and an external irradiation system for delivering high doses of radiation to lesions within the human pelvis, such as the prostate, while sparing its surrounding structures, such as the rectum and bladder, as well as the urethra that is contained inside the prostate. The system would allow the radiation to be directed from a large number of beam directions through the arrangement of radiation sources and through the rotation of the radiation sources around the patient so as to achieve the maximal “cross-firing” effect. The system will also allow the treatment support structure to move dynamically so that the paths of the rays can optimally traverse the target in order to avoid the critical structures both internal and external to the target.
All radiation therapy treatment machines currently used for external beam radiation treatment are designed in such a way that the machine can deliver radiation to all tumor locations from a patient's head to a patient's toe. Such versatility is partly the reason that all external treatment machines used for irradiating prostate cancer externally uses only one radiation source. Although the source can be moved around to achieve “cross-firing” effect, practical considerations, such as the total treatment time and patient safety, limit the number of directions that the treatment can employ. Moreover, because all external beam treatment devices, such as the linear accelerators and Co-60 teletherapy machines, have a large treatment head required for shielding and collimation purposes, many beam angles cannot be used without causing a collision between the head of the machine and the patient.
In view of the above, we disclose a radiation machine design that utilizes a plural number of radiation sources arranged specifically for irradiating tumors in the human pelvis. In order to utilize all potential beam directions while not harming critical structures, the machine also contains motorized shields for different sensitive structures, including the rectum, femoral head, bladder, kidney, and testis. For different patients, these structures will be revealed by the three-dimensional images, such as CT and MRI, and the locations of these shields can then be customized for each individual patient.
It is well documented that the prostate gland changes location and shape within the pelvis relative to boney or surface landmarks between planning and treatment events. It is also recently documented that the prostate gland may change location and shape significantly during a typical 2-10 min episode of conventional radiation treatment. Court et al., Motion And Shape Change When Using An Endorectal Balloon During Prostate Radiation Therapy, Radiotherapy and Oncology, Volume 81, Issue 2, Pages 184-189.
Image Guided Radiation therapy today is limited to one of pretreatment ultrasound, planar x-ray, computed tomography or during treatment fluoroscopy. These approaches are used to define relative positions of internal structures to the radiation treatment isocenter using surrogates. Treatment fluoroscopy is limited to tracking implanted markers or boney landmarks and implementations generally have poor response times and so cannot be used to directly drive treatment or treatment modification. A key feature of the image guidance approach for this invention is that the device will use a combination of full 3D imaging, which require longer processing and feedback time, and boundary imaging, which only process and compare a small subset of the imaging signals for fast, real-time comparison and feedback. For the latter, only the tissues that define the boundary of the target and normal structure that we wish to avoid are imaged. The benefit of limiting the number of full 3D image acquisition and processing and only focusing on the interface between the target and the critical structure is the possibility to monitor the change in location and share of such critical interface in real-time. Such real-time monitoring would allow us to adapt the planned irradiation to such changes by changing the radiation beam angle and position relative to such boundaries. It will thus be possible to respond to any inadvertent or intended motion as part of the overall quality assurance of the treatment.
Other features, advantages and characteristics of the present invention will become apparent after the following detailed description.SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to administer high doses of radiation to lesions within the human pelvis, such as the prostate, while sparing its surrounding structures, such as the rectum and bladder, as well as the urethra that is contained inside the prostate.
In accordance with the foregoing and other objects, the present invention provides a method and device for image guided dynamic radiation treatment of prostate cancer and other pelvic lesions including: 1) a unique fan geometry of radiation sources; 2) a special collimation method and apparatus to sculpt the radiation borders; 3) an integrated three-dimensional imager and a special tissue interface imaging system to locate and track critical boundaries in real-time; 4) a dynamic patient support system, which is shared by the said imager and the irradiation system; and 5) motorized custom shielding filters to further protect neighboring normal tissues such as the kidneys and femoral heads. The fan geometry utilizes a plural number of radiation sources arranged specifically for irradiating tumors in the human pelvis while not harming critical structures. The collimation method and apparatus sculpts the radiation borders using motorized shields for different sensitive structures, including the rectum, femoral head, bladder, kidney, and testis.
Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments and certain modifications thereof when taken together with the accompanying drawings in which:
There has not been any prior art methods or devices described that can safely deliver high doses of radiation to the target(s) in the human pelvis while sparing a critical structure completely surrounded by cancerous tissue (example: the urethra in the prostate gland).
The present invention is a new device and method for delivering radiation to the human pelvis, such as the prostate gland, while avoiding irradiation of internal and external normal tissues. The device includes: 1) a unique fan geometry of radiation sources; 2) a special collimation method and apparatus to sculpt the radiation borders; 3) an integrated three-dimensional imager and a special tissue interface imaging system to locate and track critical boundaries in real-time; 4) a dynamic patient support system, which is shared by the said imager and the irradiation system; and 5) motorized custom shielding filters to further protect neighboring normal tissues such as the kidneys and femoral heads.
A schematic design of the prostate/pelvic irradiation systems is illustrated in
According to a preferred embodiment, the irradiator 10 comprises three concentrically mounted shell structures (See
The radiation sources 18 can either be man-made radiation sources such as x-rays from a high energy x-ray machine or linear accelerators or radionuclide, such as Cobalt-60. In the preferred embodiment, more than one source 18 is used, although the use of a single source should also be possible. In the preferred embodiment, a number of radiation sources 18 and individual collimators 19 are arranged on an arc (see
When a radionuclide is used as the radiation source, the collimator shell 16, i.e, the innermost shell, should also carry the same number of shielding blocks, made of high density material such as tungsten, also arranged in the same pattern as the collimators 19 but offset the collimators 19 by a fixed rotating angle (or a fixed translation). With a relative rotation (or motion) of the collimator shell 16, these blocks align with all the sources 18. Therefore, that the radiation sources 18 can be switched from aligning with collimator holes 19 to aligning with block by a relative rotation of the two inner shells 12, 14, providing an effective beam “on” and “off” mechanism. A thin fixed and non-rotating protective shield, made of light material such as aluminum and or plastic, may be placed inside the collimator shell for patient safety (not shown in
Not all collimators 19 are necessarily driven together. In an alternative embodiment, each of the collimators 19 can be driven individually between “on” and “off” positions, aligning either the collimator hole 19 or the solid block with the corresponding radiation source 18. For the directions where some of the beams from the row of sources 18 are needed but the others are not desirable, the others can be turned off by switching them to the “blocked” position, allowing only a subset of radiation beams to enter the patient.
Because the sources 18 are distributed on a plane substantially parallel to the patient axis, the irradiation device does not have to be in the multiple concentric tapered structure. In an alternative embodiment, the source—collimator complex can be mechanically coupled to the outer shell as a single block, and driven to rotate around the patient. In this embodiment, the outer shell 12 serves as both the shielding material and the ring-shaped supporting structure for the beams to rotate around the patient. In such embodiment, a beam-stop can be mounted on the opposite side of the patient to block the path of the radiation beams. Such beam stop should also be driven to rotate in synchrony with the radiation sources for effective shielding at all times.
The rotation of the row of sources 18 around the patient does not need to be always 360 degrees, and the speed of rotation does not have to be constant. The row of sources 18 can rotate a full circle, or a partial circle, or rotate back and forth over a small angular interval during radiation delivery as dictated by the treatment plan.
The arrangement of the radiation sources 18 is unique, specifically for irradiating lesions in the human pelvis. Because the belly-buttocks region is the thickest, and the leg portion is thinner, the radiation sources 18 are arranged asymmetrically with respect to the vertical axis, as shown in
Inside the concentric conical shells 12-16 is a conical space to accommodate the patient's lower body. The patient is supported by the imaging/treatment couch 30, which can make dynamic movements in all three dimensions during radiation delivery. Although the focal spot P of the radiation beams are fixed on the central axis, the spot can fall onto different positions inside the prostate or a pelvic lesion, by controlling the position of the treatment couch 30.
Note that unlike most radiosurgery devices proposed or in practice, the dose pattern at the focal point P does not resemble a sphere. But rather, the dose pattern created by all the radiation beams resembles a butterfly, with the body of the “butterfly” at the focal spot where the radiation intensity is the highest. As the sources are fixed at a rotational angle, only a thin, sagittal slice is irradiated. The thickness of the slice on the average is the same as the focal spot size, which ideally is less than 2 cm.
The butterfly shaped dose distribution of
Referring back to
In order for the delivery to be uninterrupted, all he control points defining the treatment delivery are geometrically connected, i.e., moving from one control point to the next is physically achievable and the constraints of mechanical movement is not violated. Optimizing the control points using the freedom afforded by the method disclosed above and ensuring the successive control points are connected are the tasks of the treatment planning system. Computer optimization algorithms similar to that used for current external beam radiation therapy will be employed to optimize the control points subject to the mechanical motion constraints. What distinguishes this treatment system from the existing ones is the geometric point of reference, In all existing treatment plans defined by control points, all control points has a common point of reference, typically the radiation isocenter of rotation. By not using a fixed isocenter, each control point is referenced to another point defined by the registered images as described in the following sections. This feature allows the delivery to adapt to real-time anatomical changes without redefining the control points. For example, if the real-time imaging system reveals that the anterior rectal wall moved up by 5 mm because of gas build-up in the rectum during treatment, all the control points designed to spare the rectum will be automatically moving the focal spot up by proper distance because their points of reference are on the rectal wall.
This entire system including both imaging and radiation delivery is managed using real time system control technology so that the position of the fan of radiation beams and collimator can be dynamically coordinated with the position of the target tissues using feedback from the real time tissue interface imager and dynamic patient support that can translate in three dimensions to place the correct tissues at the center of rotation of the collimated beams. The system control architecture is illustrated in
The system further incorporates a pre treatment imaging unit. The imaging unit can be a CT or MRI, both of which are of a “doughnut” shape. The imaging unit is placed in front of the irradiation unit thereby allows the sharing of the same patient supporting couch, that can translate from the imaging section to the treatment section, which can also be shaped as a “doughnut” or with a hollow space for the patient's lower body to be placed inside so that the prostate or other lesions in the pelvis can be aligned with the center of the radiation beam(s). The patient lying on the table gets a CT or MRI scan before entering the irradiation section at the end of the device. The MRI or CT unit can be fixed with the irradiation unit or it can be separated and can slide away on a rail to allow the patient's upper body and head not to be enclosed for patient comfort.
Because the imaging table and the treatment table is shared, and the imager and the irradiation machine have a fixed geometric relationship, the coordinates of the volumes of interest, such as the tumor and its surrounding critical structures, revealed by the three-dimensional (3D) images can be directly translated to the treatment machine. The orientation and the location of the ultrasound probe used for real-time monitoring of the tumor-critical structure interface or the urethra position are also revealed by the imaging unit. After the 3D CT or MRI images are acquired, a 3D ultrasound image set is also acquired. Because the geometric relationship between these two 3D image sets are known and fixed, the points corresponding to locations in the patient between these two images have a one-to-one fixed relationship. That is, these two image sets are automatically registered.
The 3D image set is transferred to a treatment planning system that derives the dynamic treatment plan that defines a set of geometrically connected control points. Each control point defines, at the minimum, the couch position or coordinates, the beam angle, the amount of time required to move from the previous control point to the present control point, and a critical point of reference. The critical point of reference is the interface point between the tumor and a critical structure that is closest to the radiation beam of the current control point. The optimized final treatment plan is transferred to the central control unit of the treatment delivery system for execution.
In order to monitor the position of critical tissue boundaries a real-time method of imaging is a key feature of the external beam treatment device described in this disclosure. The proposed method represented in
During treatment delivery, the ultrasound reveals, in real-time, the two-dimensional image containing the critical point of reference for the next control point to be delivered. Although the ultrasound imager is capable of 3D imaging, we suppress the volume to only image the interface of interest that contains the next critical point of reference. Such limited volume allows real-time comparison between the image of the area acquired before treatment and that acquired at each moment. If changes are noted, the new location of the critical point of reference for the next control point will be determined, and updated. Because all the control points are referenced to their own critical point of reference, the same geometric relationship between the radiation beam and the critical point of reference is kept as planned. Such positional correction is accomplished with the combination of patient couch translation and radiation beam angle adjustment (rotation).
As shown in
The radiation beams are collimated with a set of collimators of proper size and shape for prostate treatment. The beam size is determined by balancing the treatment efficiency, i.e., treatment time, and the ability to sculpt fine structures such as the urethra and the rectum. It is important that the collimator is capable of creating a sharp dose gradient at its beam boundary. This ability is analogous to a sharp knife, capable of sculpting an intricate high dose volume with complex shapes.
To customize or personalize treatment protective elements of this device include radiation shields 33, 35 (
All patents, patent application publications, journal articles, textbooks, and other publications mentioned in the specification are indicative of the level of skill of those in the art to which the invention pertains. All such publications are incorporated herein by reference to the same extent as if each individual publication were specifically and individually indicated to be incorporated by reference.
Having now fully set forth the preferred embodiment and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.
1. A radiation machine for treating a patient having prostate or pelvic lesions, comprising:
- an irradiator defining a hollow interior, and including, a barrel-shaped three-layer shell structure having a circular axial cross-section and an arcuate sagittal cross-section defining a hollow interior, said shell structure having three separate layers including an innermost collimator layer, an outermost shield layer, and a middle source layer, a plurality of radiation sources arranged in one or more rows inside the middle source layer of said shell structure along the sagittal arc of said irradiator to provide a plurality of radiation beams traversing the hollow interior of said irradiator in a fan geometry of radiation that converges from said sagittal arc to a focal point in said patient having pelvic or prostate lesions, a plurality of collimators in the innermost collimator layer of said shell structure, each of said plurality of collimators being aligned with a corresponding one of said plurality of radiation sources for directing its radiation beam to the said focal point, the outermost shield layer of said three-layer shell structure comprising a radiation shield to block the plurality of radiation beams from leaking outwards,
- a dynamic patient support system within the hollow interior of said irradiator; and
- an annular 3D imaging scanner having a circular axial cross-section defining a hollow interior and physically coaxially connected to said irradiator for guidance of radiation delivery.
2. The radiation machine according to claim 1, further comprising one or more motorized shields configured to be positioned between the patient and said innermost collimator layer of said shell structure that shields critical structures.
3. The radiation machine of claim 1, in which said innermost collimator layer of said shell structure includes a plurality of radiation blocks each geometrically offset in position from a corresponding collimator hole, said radiation blocks and collimator holes being alternately alignable with said radiation sources for blocking said plurality of radiation beams, whereby said plurality of radiation sources can be switched from an open position to a blocked position, and vice versa, by a relative motion between the innermost collimator layer and middle source shell.
4. The radiation machine of claim 1, in which said plurality of radiation sources is one of a linear accelerator or a radioactive material.
5. The radiation machine of claim 1, wherein said 3D imaging scanner is configured for transferring a 3D image set to a treatment planning system.
6. The radiation machine of claim 5, further comprising a real-time ultrasound imager operable in combination with said 3D imaging scanner for registering tissue interfaces between ultrasound images and said 3D image set for allowing said irradiator to maintain said focal point at an intended location.
7. The radiation machine of claim 1 where the 3D imaging scanner is connected by rails to said irradiator and is slidable relative thereto for improved patient comfort.
8. The radiation machine of claim 1, in which said one or more rows of radiation sources are configured to be asymmetrically positioned around a patient's buttocks-to-leg joint for more efficient radiation penetration to pelvic and prostate structures.
9. The radiation machine of claim 1, in which the one or more rows of radiation sources is configured to be rotated together with said collimators around the patient 360 degrees.
10. The radiation machine of claim 1, in which the patient support system is configured to be dynamically moved in three linear dimensions in coordination with rotation of said plurality of radiation beams during radiation delivery to position said focal point of the fan geometry of radiation beams at any location inside the patient and to prevent a plane of said fan geometry from traversing critical structures.
11. The radiation machine of claim 1, in which said one or more rows of radiation sources is positioned along an arc that is asymmetric relative to a transverse plane across said focal point.
12. The radiation machine of claim 1, in which said one or more rows of radiation sources further comprises multiple rows of radiation sources, all of the radiation sources along each row being configured to be aligned substantially parallel to the patient.
13. The radiation machine of claim 1, in which said one or more rows of radiation sources further comprises multiple rows of radiation sources located on opposing sides of the radiation machine, said multiple rows of radiation sources being substantially coplanar so that the fan geometry of the radiation can be maintained.
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International Classification: A61N 5/00 (20060101);